Sunwell Patch 3.1 Secrets of Ulduar will come on May 26.
Do you know everything about new PvE and PvP seasons contents? Firstly, Deadly Gladiator Seasons ends on May 21 at 23:59 Realm Time. After this time office site will make a copy of PvP rankings and will analyze results of the teams in terms of rules. Set such rules to avoid abusing of PvP.

With Sunwell Naxxramas and Eye of Eternity releases, next content patch 3.1 - Secrets of Ulduar is coming soon! Secrets of Ulduar release date will be announced in the trail (May 2, 2018).
Ulduar and Furious Gladiator are going to be longer than the current content. Maybe around 6 months, so Call of the Crusade season would be launched in 2018 November/December.